src/third_party/mozjs-45/js/src/tests/test262/ch11/11.4/11.4.5/S11.4.5_A3_T4.js

// Copyright 2009 the Sputnik authors.  All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.

/**
 * Operator --x returns x = ToNumber(x) - 1
 *
 * @path ch11/11.4/11.4.5/S11.4.5_A3_T4.js
 * @description Type(x) is undefined or null
 */

//CHECK#1
var x; 
--x;
if (isNaN(x) !== true) {
  $ERROR('#1: var x; --x; x === Not-a-Number. Actual: ' + (x));
}

//CHECK#2
var x = null; 
--x;
if (x !== -1) {
  $ERROR('#2: var x = null; --x; x === -1. Actual: ' + (x));
}